System for Locking a Mounting Ring on a Vehicle Hub

ABSTRACT

A locking system for a ring for mounting on a hub of a vehicle, the mounting ring being intended to receive a bead of a tire in an assembly for mounting the tire on the hub of a vehicle. The locking system comprises a locking ring and a polymeric insert.

The invention relates to a locking system for a ring for mounting on ahub of a vehicle, the said mounting ring being intended to receive abead of a tire, particularly of the “tubeless” type, that is to say atire that has no separate air chamber.

A mounting assembly such as this is more particularly intended to befitted to heavy vehicles of the earth-moving and construction vehicletype for example, such as those used in mines.

The customary embodiments of running gear are of two types as far as thewheel rims are concerned. They are produced either with what are knownas drop-centre rims, which have tapered bead seats inclined by an angleof 5° or 15° with respect to the axis of rotation of the assembly, orwith flat or practically flat base rims which have bead seats inclinedeither by 0° or by 5° with respect to the axis of rotation.

Drop-centre rims have a mounting groove the diameter of which ismarkedly smaller than the nominal diameter of the rim. This internaldiameter of the rim is considered by users to be too small because itdoes not, for example, allow brake drums to be selected that are of asize suited to effective braking of vehicles which are becomingincreasingly powerful with respect to their weight.

As a result, the said rims are commonly used for mounting and running,for example, tires of passenger vehicles and/or heavy goods vehicles,but are used far less, if at all, for other types of vehicles such as,for example, earth-moving and construction equipment.

In order to fit tires, particularly tires of the tubeless type, a flatbase rim requires there to be at least one removable lateral ring, alocking ring and a seal, and obviously the base of the rim to have afixed flange on the opposite side to the side on which the parts areremovable. This is because the dimensions of the wheels of the vehiclesand the dimensions of the tires, particularly the stiffness of the lowerregions, entail producing the said wheels in multiple parts so as toallow the tire to be mounted on a rim. It is therefore necessary to haveat least three parts. In most cases, the number of parts needed isgreater than three and may sometimes be as many as six parts forlarge-sized tires, not including the parts needed to fix the wheels tothe vehicle. With the exception of the seals which are made of rubber,the parts of a wheel rim are made of metal and are therefore heavy,bulky and difficult to handle. It therefore follows that mounting andremoving large and very large tires are difficult and lengthyoperations. Fitting and/or removing a wheel equipped with such a tireinvolves laying up the vehicle or the equipment for a length of timethat is rather considerable and therefore prejudicial to the desiredproductivity in the use of these vehicles.

Patent Application WO 00/71365 describes a technique that allows themounting of tires to be simplified, these tires being mounted directlyon the hub which then acts as a rim. Independent mounting rings act asthe bead seats and are held in place by lock rings which can be securedto the hub using, in particular, complementary profiles. With thistechnique, the locking ring is made up of a vulcanized rubber compoundreinforced by and coated onto a reinforcing ring that iscircumferentially elastic and radially resistant to compression.

A technique such as this is very advantageous because it makes itpossible to eliminate the phases of mounting onto a rim and of fixing awheel to the vehicle, the tires being mounted directly onto the hub viathe mounting rings and locking rings. Furthermore, since the number ofelements is greatly reduced, the phases involved in handling theseelements become simpler.

Tests conducted on this type of technique have revealed the fact thatthe locking ring, which, aside from its function of locking the system,is an element involved in the transmission of braking or driving torque,undergoes loading which causes it to wear. The locking ring which, atits surface, exhibits a rubber compound in order to give it elasticityand provide control over the coefficients of friction, particularlybetween the hub of the vehicle and the locking ring, therefore in use issubjected to wearing of its outer part which comes into contact with thehub on the one hand, and a mounting ring on the other hand, both ofthese being made of metal. This wear results in the need to change thelocking ring each time the tire is changed. The complex nature of thiselement which is made up of a rubber compound coating an annularreinforcing element that is resistant to compression and the need tochange it periodically leads to additional costs that must be borne bythe user.

The inventors have therefore set themselves the task of improving thetechnique disclosed in document WO 00/71365 and, in particular, oflimiting the costs associated with operating and maintaining thistechnique.

This objective has been achieved according to the invention using alocking system for a ring for mounting on a hub of a vehicle, the saidmounting ring being intended to receive a bead of a tire in an assemblyfor mounting the said tire on the said hub of a vehicle, the saidlocking system consisting of a locking ring and a polymeric insertintended to be placed between the hub and the locking ring.

A polymeric insert must be understood to mean an insert consistingessentially and, in particular, for the most part, of at least onepolymer compound.

The polymer compound is advantageously a compound containing vulcanizedrubber, that is to say a blend of elastomer(s), reinforcing fillers andadditives, all of which are well known, that is then vulcanized at acertain temperature.

The polymeric insert advantageously has a secant elastic modulus of atleast 1 MPa under a relative elongation of 10%, making it possible inparticular for it to be placed on the hub more easily.

The inventors have demonstrated during their studies that the limitationin torque transfer between the hub and the tire could be ascribed toslippage between the hub and the locking system of the mounting ring.Specifically, studies consisting in reducing the friction coefficientsof the materials have shown that the slippage was essentially observedat the point of contact between the locking ring and the hub. Thiseffect may in particular be explained by the mean radius of the contactzone between the hub and the locking ring being less than the meanradius of the contact zone between the locking ring and the mountingring. This difference in mean radius, and consequently difference incontact area, and hence difference in friction surface between thevarious torque transfer regions, is compensated for in accordance withthe invention by an appropriate choice of the friction coefficients andin particular by the use of a polymeric insert between the hub and thelocking ring.

The locking system thus produced according to the invention makes itpossible, in particular during a tire change, to change at the same timethe polymeric inserts each associated with the locking rings, which maybe damaged, but to keep the locking rings for a new use.

According to a preferred embodiment of the invention, the locking ringis made of an incompressible material.

A ring that is said to be incompressible or radially resistant tocompression must be understood to mean a ring in which the maximumradial dimension of its transverse section, that is to say the longestradial distance between two points on the contour of the said sectionand situated on a normal to the axis of rotation of the rim, is reducedunder load by 2% at most. For example, the ring can be a metal ring.

An incompressible locking ring may a priori be used throughout thelifetime of the vehicle.

The locking ring is advantageously circumferentially elastic. A ringthat is said to be circumferentially elastic must be understood to meana ring in which the circumferential development is capable oflengthening by at least 3% under a load of 50 daN at most, and ofreturning to its initial state when the load is removed. The lockingring thus allows simplified handling for fitting it in the mountingassembly, while at the same time gripping the polymeric insert and thehub of the vehicle.

The circumferential direction, or longitudinal direction, of the tire isthe direction corresponding to the periphery of the tire and defined bythe direction in which the tire runs.

The transverse or axial direction of the tire is parallel to the axis ofrotation of the tire.

The radial direction is a direction intersecting the axis of rotation ofthe tire and perpendicular thereto.

The axis of rotation of the tire is the axis about which it rotatesunder normal use.

A radial or meridian plane is a plane containing the axis of rotation ofthe tire.

The circumferential meridian plane or equatorial plane is a planeperpendicular to the axis of rotation of the tire and which splits thetire into two halves.

According to one advantageous embodiment of the invention, the lockingring consists of a collection of several, preferably identical,individual elements joined together to form the said ring. An embodimentsuch as this in particular allows for simplified handling and simplifiedtransportation of the locking ring since the individual elements can behandled independently of one another.

Advantageously too, each individual element is such that it correspondsto a sector representing between 5 and 60° of the locking ring when thelatter is in place in the assembly for mounting the tire on the hub ofthe vehicle. The locking ring, when fitted in the assembly for mountinga tire on a hub, fits partially into a recess made on the hub. Thisrecess has an axially outer part which exhibits a slope which inparticular allows the transmission of torque. The position of thelocking ring can vary slightly in the axial direction along the saidslope of the recess while the tire is being mounted. An individualelement representing a sector of between 5 and 60° can be produced witha longitudinal curvature such that the individual element does notdamage the polymeric insert regardless of the position of the saidindividual element along the slope of the recess, and thereforeregardless of the radius at which it lies. Elements of longer lengthwith a given curvature may, in certain positions, bear against thepolymeric insert via their ends and therefore run the risk of damagingthis envelope on account of high localized pressure. When the individualelements are made of metal, each individual element advantageouslyrepresents a sector of between 5 and 30°.

One preferred embodiment of the invention makes provision for theindividual elements to be joined together by additional elementscomprising elongating means associated with an elastic restoring force.An embodiment such as this allows the locking ring to be given someelasticity and thus allows the pressure to be distributed uniformlyaround the entire periphery of the said element.

A locking ring according to the invention is considered to have at leasttwo walls: a radially inner wall and a radially outer wall, the said twowalls possibly being connected by lateral walls that are practicallyperpendicular to the direction of the axis of rotation. The radiallyinner wall has a shape similar to the shape or profile of the recessesor grooves created on the hub of the piece of equipment in order toreceive the said rings. The said recesses may, when viewed in meridiansection, have any shape but preferably have a meridian section thesurface of which is almost triangular with a base along the generatrixof the hub and with two sides making acute angles ranging between 10°and 45° with the direction parallel to the axis of rotation, the twosides being connected, at their opposite ends to the said base, by arounded vertex, so as to minimize stress concentrations and the risk offatigue cracking. The quasi-height of the said triangle, shortened bythe rounded vertex on the said base, preferably ranges between 10 and 45mm. The radially inner wall of the locking ring in meridian section hasa profile identical to the interior profile of the quasi-triangledescribed hereinabove.

The meridian section of the reinforcing ring of the locking ring, in itsradially inner part, may be of any shape in as much as a substantialpart of the maximum radial dimension of its meridian section lies insidethe triangular section of the recess formed in the hub. The expression“substantial part” must be understood to mean a radial distancerepresenting at least 25% of the maximum radial dimension of the sectionof the locking ring.

According to an alternative embodiment of the invention, the meridiansection of the locking ring is, in its radially inner part, polygonalwith at least two sides substantially parallel to the two sides of thetriangular section of a recess made on the hub of the vehicle, and atleast 25% of the maximum radial dimension of the meridian section of thering lies within the triangular section of the said recess formed in thehub.

Advantageously, the meridian section of the locking ring is, in itsradially outer part, polygonal with at least one tapered part thegeneratrix of which makes an angle that may range between 15° and 45°with respect to the direction of the axis of rotation. The said taperedpart will then, when the tire is being mounted, come to face the taperedpart of the radially inner wall of the mounting ring on which the beadof the tire will be mounted.

In order to make the operations of removing the tire easier, the saidlocking ring is advantageously equipped with and/or associated with acord or strap, for example a metal one, allowing the ring to bedislodged from the recess in the hub by pulling on the said cord.

According to a preferred embodiment, the polymeric insert extends incontact with the radially inner wall of the locking ring.

One advantageous embodiment of the invention provides for the polymericinsert to extend over the axially inner side wall of the locking ring.According to this embodiment, the insert in particular favours thefitting of the mounting ring by inflation by forming what is called a“primary” seal, which makes it possible to start the inflation.

Also advantageously, the polymeric insert includes an extension which ispositioned beyond the radially outer end of the axially inner side wallof the locking ring. This extension of the polymeric insert forms acircumferential protuberance that forms a primary seal at the contact ofthe mounting ring before inflation and further facilitates inflation byforming the “primary” seal.

The mounting ring is an element, for example made of metal, made up of arim seat, generally tapered but which could be cylindrical, or someother shape, the said seat being extended axially and radially outwardsby a rim flange, it being possible for the said flange optionally to beindependent of the seat and removable from the said seat. The saidmounting ring advantageously has a radially inner wall formed of atleast one tapered part the generatrix of which makes an angle rangingbetween 15° and 45° with the direction of the axis of rotation, whilethe radially outer wall, when viewed in meridian section, is made up, onthe one hand, of a tapered generatrix forming an angle that may rangebetween 0° and 16° with the direction of the axis of rotation and, onthe other hand, extending the said generatrix axially outwards via anarc of a circle, of the curve that represents the axially inner andradially outer profile of the rim flange. In all cases, the said curveis advantageously situated radially on the outside and axially on theinside of a segment of straight line joining the point of intersectionof the said curve with the tapered generatrix mentioned hereinabove andthat point on the said curve that is furthest from the axis of rotation.Thus, the said curve may be formed of an arc of a circle tangential tothe arc of a circle connecting the tapered generatrix with the curve. Itmay also be formed of a segment of a straight line which may or may notbe perpendicular to the axis of rotation, tangential radially on theinside to the above connecting arc and radially on the outside to asecond arc of a circle so as to obtain the desired curve. The mountingrings may be independent of the tire and, more specifically, of thebeads of the said tire. To facilitate and speed up mounting and removaloperations, and the various handling operations required, the mountingrings with seats and flanges form an integral part of the tire just as,for example, do the bead wires; the said rings may be secured to thebeads of the tire by press-fitting without the possibility ofdetachment. A principle such as this is described in the applicantcompany's Patent FR 2 087 770.

Whether or not they are secured to the beads of the tire, and with aview to allowing the elements that have to be fitted to be handled moreeasily, the mounting rings are advantageously equipped in their axiallyinner parts with a lifting system, for example of the type involving anairbag, which makes it possible to create and maintain, during fittingoperations, a circumferentially constant gap between the hub and theradially inner part of the rings, hence greatly improving the latitudefor axial movement. The said 5 to 20 mm gap also has the purpose ofallowing the tire/mounting ring assembly to be engaged by sight on thehub without binding. Another alternative embodiment of the invention forfacilitating the fitting of the mounting rings, and of the locking ringsand/or the tires, anticipates variations in diameter of the hub. Withthis alternative embodiment, the radial distance between the hub and theradially inner part of the rings and/or the beads of the tire isincreased in those axial regions where contact is not required, that isto say in those regions where there are no recesses for receiving thelocking rings.

Other details and advantageous features of the invention will becomeapparent hereinafter from the description of an exemplary embodiment ofthe invention given with reference to FIGS. 1 to 4 which depict:

FIG. 1: a schematic depiction in meridian section of an assembly formounting a tire on a hub according to the invention;

FIG. 2: a schematic depiction in meridian section of the locking systemaccording to the invention;

FIG. 3: a schematic depiction in circumferential section of part of thelocking ring according to one embodiment of the invention;

FIG. 4: a schematic depiction in circumferential section of analternative embodiment of an element used to connect two individualelements.

For easy understanding, the figures are not drawn to scale.

FIG. 1 shows only the bead 1 of a large tire intended to be fitted to apiece of construction equipment. The said bead 1 is mainly reinforced bya bead wire 2 around which the radial carcass, not depicted in FIG. 1,of the said tire is wound to anchor it. The bead 1 has radially innerand axially outer walls of shapes and sizes designed to be mounted on amounting ring 3 made up of a tapered seat 31 of which the generatrix310, viewed in meridian section, makes an angle of about 5° with thedirection of the axis of rotation, this generatrix being extendedaxially outward by a wall 320 of a rim flange 32, the said wall 320being perpendicular to the direction of the axis of rotation and endingaxially and radially on the outside in a rounded portion 321. As for theradially inner wall of the tapered mounting ring 3, it is formed of anessentially cylindrical first part 311 intended to sit on thecylindrical surface of a hub 4 and of a second part 312 intended to comeinto contact with the radially outer wall 51 of the locking ring 5, thesaid wall 51 being of a shape that complements that of the wall 312. Thesaid locking ring 5 thus has a radially outer surface 51 intended to bein contact with the radially inner surface 312 of the mounting ring 3and a radially inner surface formed of two generatrices 52, 53 which isinserted in a recess 6 of the hub 4, the shape of the said recess 6complementing the surface formed by the two generatrices 52, 53 of thelocking ring 5. Upon assembly, the two generatrices 52, 53 come to bearagainst the two tapered generatrices 61, 62 of the recess 6 created inthe hub 4, via a polymeric insert 7. The generatrices 61, 62 of therecess 6, with the continuation of the cylindrical generatrix 41 of thehub 4, form a triangle with two sides 61, 62 and a base of sufficientaxial width that at least one third of the locking ring 5 lies insidethe triangle defined above, thus, in conjunction with the shape of therecess 6 and the radially inner and outer shapes of the locking ring 5,providing enough axial retention to retain the said ring 5 under allrunning conditions.

FIG. 2 shows a locking system 20 consisting, on the one hand, of thelocking ring 25 and, on the other hand, of the polymeric insert 27. Thepolymeric insert 27 of annular shape is inserted between the recess 26provided for this purpose in the hub 24 and the locking ring 25.

In the case shown in FIG. 2, the insert 27 is provided with a part 28bearing on a cylindrical part of the hub 24 so that said insert 27 isproperly positioned. The part 28 of the insert 27 also has a taperedaxially inner end in order to make it easier for the mounting ring 23 topass.

The insert 27 also includes a positioning end 29 which radially extendsto the outside of that part of the insert 27 which comes into contactwith the axially inner side wall of the locking ring 25. Before fittingthe mounting ring 23, this end of the insert 27 is advantageously in theposition represented by the hatched zone 29′. This position 29′ of thisend of the insert 27 enables the “primary” seal in contact with themounting ring 23 to be formed in order to initiate the inflation of thefitting assembly. The position 29 of this end is obtained duringinflation, the mounting ring bearing on said insert 27.

The locking ring and the mounting ring may also have complementaryshapes in an axially inner zone 30 allowing in particular an axialblocking function, preventing movement towards the outside of themounting ring on the locking ring. This blocking function also makes itpossible to limit the compression of the insert 27 in this zone 30. Thisblocking, possibly also combined with axially outward extension of thelocking ring, may also help to control the positioning of the mountingring along the radial and axial directions and in particular prevent anyrisk of non-uniform positioning around the wheel.

FIG. 3 depicts part of a locking ring and, more specifically, two of theindividual elements 33, 34 of which it is formed, the said elementsbeing connected by a connecting element 35.

The locking ring thus advantageously consists of a collection ofseveral, preferably identical, individual elements 33, 34 joinedtogether to form a reinforcing ring. This embodiment in particularallows for simplified handling and simplified transportation of thelocking ring. The individual elements 33, 34 may be combined on sitewhen the tire is being mounted on a vehicle. Handling and transportingthe locking ring is thereby simplified.

Each individual element 33, 34 corresponds to a sector representingbetween 5 and 60° of the locking ring when the latter is in place in theassembly for mounting the tire on the hub of the vehicle. This smallsize of the individual elements 33, 34 will make it possible, whenfitting the tire on a hub, to avoid any risk of damaging the polymericinsert 7, 27. This is because the locking ring 5, 25 which fitspartially into a recess 6 on the hub has, particularly when the tire isbeing fitted, to move over the axially outer part of the said recess 6,which has a slope. The position of the locking ring 5, 25 thus variesaxially along the said slope of the recess while the tire is beingmounted and therefore has a changing radial position. An individualelement corresponding to a sector representing between 5 and 60° isproduced with a longitudinal curvature such that the said individualelement does not damage the polymeric insert irrespective of itsposition along the slope of the recess, and therefore of the radius ofcurvature at which it lies. When an individual element is made of metal,since the flexibility of metal is low, it advantageously corresponds toa sector representing less than 30°. The length of the individualelement, that is to say the length of the sector to which itcorresponds, will be defined according to the nature of the materialused. Whatever the nature of the material of which the individualelements are made, these elements may also have axially-oriented andnarrow cuts to make the said individual elements more flexible in theradial direction and thus minimize any risk of damaging the polymericenvelope.

The connecting element 35 which connects the individual elements 33, 34together has means of elongation associated with an elastic restoringforce. In FIG. 3, the element 35 is thus produced in the form of acomponent, preferably a metal component, fixed, at the points 36, 36′,to each of the elements 33, 34, one on each side. Attachment is by anymeans known to those skilled in the art. Advantageously, the element 35penetrates depressions 37, 37′ in each of the elements 33, 34 andprovided for this purpose at their ends. The element 35 furthercomprises an elongation system 38 with an elastic restoring force. Thissystem 38 is, for example, as depicted in FIG. 3, produced using amoving part 39 that can move in the circumferential direction, the saidmoving part being associated with the attachment point 36′. The movementof this part 39 makes it possible to lengthen the distance between thetwo elements 33, 34 and thus corresponds to a circumferentiallengthening of the locking ring 5, 25. As it moves, the moving part 39compresses a spring 40 which creates a restoring force and thereforegives the abovementioned circumferential elongation of the locking ringan elastic nature.

FIG. 4 depicts, in circumferential section and as in the case of FIG. 3,part of a locking ring and, more specifically, two of the elements 33′,34′ of which it is composed, the said elements being connected by aconnecting element 35′. The connecting element 35′ comprises means ofelongation associated with an elastic restoring force; it in particularconsists of a cable 41, 41′, 41″, preferably a metal cable, of cablefixing elements 42, 43, 42′, 43′ and of blocking means 44, 45, 44′, 45′for blocking the fixing elements in the individual elements 33′, 34′. Aspring 46, 46′ is advantageously interposed between the fixing element43, 43′ and the blocking means 45, 45′ in order to provide a restoringforce in the event that the locking ring is circumferentially extended.The cable fixing elements 42, 43, 42′, 43′ are, for example, crimpedonto the cables. The blocking means 44, 45, 44′, 45′ are any elementknown to those skilled in the art and are advantageously introduced fromthe outside of the individual elements 33′, 34′; they have a shape suchthat they can retain the cable fixing elements 42, 43, 42′, 43′ while atthe same time not impeding the passage of the cable 41, 41′, 41″. Theindividual elements 33′, 34′ have a duct passing through them in thecircumferential direction, this duct for example being of circular crosssection and having the same diameter as the fixing elements 43, 43′, asdepicted in FIG. 4.

Whatever the way in which the connecting element 35, 35′ is embodied,such as the ways depicted by way of example in FIGS. 3 and 4, the sametype of fixing element can be used for joining together all theindividual elements that make up the locking ring. However, according tocertain alternative forms of embodiment, the invention anticipates thefinal connection, that is to say the final assembly between twoindividual elements that forms the assembly into a continuous annularelement, to be achieved using a simplified connecting element thatpossibly does not have any means of elongation associated with anelastic restoring force; this may, for example, involve a mechanicalcomponent of the bracket type which is inserted in slots made for thatpurpose on each end of the last two individual elements to be joined inorder to form the locking ring.

The small size of the individual elements 33, 34, the fact that they areall advantageously chosen to be identical and that they are connected byconnecting elements 35, 35′ which are also all identical and, inparticular, exhibit identical restoring forces, make it possible toobtain a uniform distribution of the pressure on the hub and thereforeon the one hand optimize the mounting of the tire on the hub and, on theother hand, optimize the operation of the tire, particularly where thetransmission of torque is concerned.

The invention as has just been described in particular with reference tothe exemplary embodiments must not be interpreted as being restricted tothese exemplary embodiments. The various elements that make up theassembly for mounting the tire may be embodied in different ways whilestill falling within the scope of the invention.

The hub may, for example, have a region of a diameter greater than itsmean diameter, for example to leave space for a braking device. Thislarger-diameter region may advantageously be provided under the regionwhere the axially inner bead of a tire is fitted. The mounting rings andpossibly the locking rings which are intended to be associated with eachof the beads of a tire may then have different meridian sections; itmust then be understood that the region that forms the place where thebeads of the tire are housed preferably remains similar for bothmounting rings so that the tire remains of conventional and, inparticular, symmetric, design.

1. A locking system for a ring for mounting on a hub of a vehicle, themounting ring being intended to receive a bead of a tire in an assemblyfor mounting the tire on the hub of a vehicle, wherein the lockingsystem comprises a locking ring and a polymeric insert.
 2. The lockingsystem according to claim 1, wherein the locking ring is made of anincompressible material.
 3. The locking system according to claim 2,wherein the locking ring is made of metal.
 4. The locking systemaccording to claim 1, wherein the polymeric insert extends in contactwith at least the radially inner wall of the locking ring.
 5. Thelocking system according to claim 4, wherein the polymeric insertextends along the axially inner side wall of the locking ring.
 6. Thelocking system according to claim 5, wherein the polymeric insertincludes an extension that is positioned beyond the radially outer endof the axially inner side wall of the locking ring.
 7. The lockingsystem according to claim 1, wherein the locking ring consists of acollection of several, preferably identical, individual elements joinedtogether to form the said locking ring.
 8. The locking system accordingto claim 7, wherein each individual element is such that it correspondsto a sector representing between 5 and 60° of the locking ring when thelatter is in place in the assembly for mounting the tire on the hub ofthe vehicle.
 9. The locking system according to claim 7, wherein theindividual elements are joined together by additional elementscomprising elongating means associated with an elastic restoring force.10. The locking system according to claim 7, wherein the meridiansection of the locking ring is, in its radially inner part, polygonalwith at least two sides substantially parallel to the two sides of thetriangular section of a recess made on the hub of the vehicle, and atleast 25% of the maximum radial dimension of the meridian section of thering lies within the triangular section of the said recess formed in thehub.
 11. The locking system according to claim 10, wherein the meridiansection of the locking ring is, in its radially outer part, polygonalwith at least one tapered part the generatrix of which makes an anglethat may range between 15° and 45° with respect to the direction of theaxis of rotation.